In a diagonal generating method, an axial feed of the tool takes place in addition to the axial feed of the workpiece during the machining of the workpiece so that different regions of the tool are used for the machining of the workpiece during the machining process. The term “axial feed of the tool” is to be understood as a relative movement between the tool and the workpiece in the direction of the longitudinal axis of the tool; the term “axial feed of the workpiece” is to be understood as a relative movement between the tool and the workpiece in the axial direction of the workpiece. In this respect, the most varied axes of a gear manufacturing machine used for carrying out the method can be used to produce these relative movements. Only the tool can, for example, be moved both in the direction of its axis and in the direction of the axis of the workpiece. Since it is a generating process, the rotary movements of the workpiece and the tool are coupled to one another. The workpiece can in particular be a gear.
Different regions of the tool successively come into contact with the workpiece during the gear manufacturing in the diagonal generating method due to the axial feed of the tool, which is also called shifting. Such diagonal generating methods are typically used to achieve a wear of the tool surface which is as uniform as possible.
It is known from DE 10 2012 015 846 A1 to provide a modification of the surface geometry of the workpiece, which has a constant value at least locally in a first direction of the workpiece and is given in a second direction of the workpiece which extends perpendicular to the first direction by a function f(x), by a corresponding modification of the surface geometry of the tool.
It is the object of the present disclosure to further develop the known diagonal generating methods. In this respect, the flexibility in the manufacture of modifications may be increased.
This object in accordance with the present disclosure is satisfied by the independent claims of the present disclosure. Advantageous embodiments of the present disclosure form the subject of the dependent claims.
The present disclosure shows a method for the gear manufacturing machining of a workpiece by a diagonal generating method in which the workpiece is gear tooth machined by the rolling off of a tool. In this respect, an axial feed of the tool with a diagonal ratio given by the ratio between the axial feed of the tool and the axial feed of the workpiece takes place during the machining. Provision is made in accordance with the present disclosure that the tool has a conical basic shape.
The inventor of the present disclosure has recognized that the flexibility in the course of the diagonal feed generating machining can be improved with respect to the previously used tools having a cylindrical basic shape by a tool which has a conical basic shape.
The tool in accordance with the present disclosure having a conical basic shape may have involute teeth which can, however, optionally have a modification. Involute gear teeth have a geometry which is produced by the generating machining step between a cylinder and a rack. The conical basic shape is produced in that the axis of rotation of the cylinder is tilted toward the main plane of the rack in the course of this generating machining step.
The method in accordance with the present disclosure may be used for the manufacture of a workpiece having a corrected gear tooth geometry and/or a modified surface structure, wherein a corresponding modification on the surface of the workpiece is further optionally produced by means of a specific modification of the surface geometry and by means of a mapping of the surface of the tool onto the surface of the workpiece, the mapping produced by the diagonal generating method.
In this respect, there is a point contact between the surface of the workpiece and the surface of the tool in the course of the diagonal generating method, wherein each point on the machined surface of the workpiece is machined by another point on the surface of the tool by the respective axial feeds. The mapping which hereby results can be used to modify the surface geometry of the workpiece via a specific modification of the surface geometry of the tool.
The inventor of the present disclosure has recognized in this connection that this relationship known for cylindrical tools and workpieces also applies to tools having a conical basic shape and to cylindrical or conical workpieces. The inventor of the present disclosure has furthermore recognized that particular advantages especially result in such a method for the manufacture of a workpiece having a corrected gear tooth geometry and/or a modified surface structure by the use of a tool having a conical basic shape. The conical basic shape in particular allows additional modifications which would not be possible with a cylindrical tool. This is founded on the fact, on the one hand, that a further degree of freedom is provided with the cone angle of the tool. Certain parameters of the macrogeometry of the tool and of the machining process furthermore influence the modifications on the right and left tooth flank differently in each case in the event of the use of a conical tool so that different modifications on the right and left tooth flanks of the workpiece are also possible on a two-flank processing by a corresponding selection or setting of these parameters.
The specific modification of the surface geometry of the tool is optionally produced in that the position of the dresser to the tool is varied in dependence on the angle of rotation of the tool and/or on the tool width position during dressing in addition to the delivery required by the cone angle. A variety of modifications can hereby be produced by a particularly simple method.
The dressing of the tool can take place on one flank or on two flanks. A profile roller dresser may be used by means of which the tool is dressed. The dressing can take place in one or more strokes.
The form roller can in particular be in contact with the tooth of the tool from the root region to the tip region during dressing so that the modification takes place in one stroke over the total tooth depth.
The profile roller dresser during the dressing can alternatively only be in contact with the tooth of the tool in part regions between the base and the tip so that the modification takes place in a plurality of strokes over the tooth depth.
The dressing of the tooth tip can take place via a tip dressing tool. A separate tip dressing tool, for example a dressing plate or a tip dressing roller, can be used in this respect. Alternatively, the tip dressing tool can be combined together with the profile roller dresser used for the dressing of the flank to form a combined dresser. The dressing of the tooth tip can therefore take place either in a separate stroke or together with the dressing of the tooth flank.
The alignment of the active surface of the tip dressing tool may be adapted to the cone angle of the tool in this respect. The tip dressing tool can in particular be tilted into a plane which extends tangentially to the enveloping surface of the cone. If a dressing plate is used, it is accordingly arranged in parallel with the enveloping surface of the cone. If a tip dressing roller is used, its axis of rotation can be aligned at an angle to the axis of rotation of the tool which corresponds to the cone angle. The axis of rotation of the tip dressing tool can alternatively remain aligned in parallel with the axis of rotation of the tool and a cone angle can be provided in the design of the active surface of the tip dressing tool. In a combination dresser, the part forming the tip dressing tool may be arranged in a correspondingly tilted manner at the combination dresser.
The present disclosure can in principle also be used with non-dressable tools. In this case, the modifications of the tool are already produced during the manufacture of the tools and can not be changed during the machining process of a workpiece.
In case of a non-dressable grinding tool, the inventive modification of the surface geometry can be produced during the manufacturing process in exactly the same way as described in the following for dressable tools, with the only change that instead of a dressing tool, a corresponding manufacturing tool is used, for example a rolling die.
In case that the tool is a hobbing cutter, it has to be manufactured in such a way that the enveloping body of the hobbing cutter has the modification provided by the present disclosure. With respect to a hobbing cutter, the term “modification of the surface geometry of the tool” as used in the context of the present disclosure is to be understood as a modification of the surface geometry of the enveloping body of the hobbing cutter.
The present disclosure may, however, be used with a dressable tool. In particular, the modification of the surface geometry of the tool may be generated during a dressing step.
The modification of the surface geometry of the workpiece in accordance with the present disclosure can have a constant value on the tooth flank in the generating pattern at least locally in a first direction of the workpiece and can be given by a function FFt2 in a second direction of the workpiece which extends perpendicular to the first direction. The local region may be a region of 5-10% of the surface area, in one example.
The modification of the surface geometry of the tool used for producing the modification of the surface geometry of the workpiece can furthermore have a constant value in the generating pattern at least locally in a first direction of the tool and can further optionally be given by a function FFt1 in a second direction of the tool which extends perpendicular to the first direction. The function FFt1 on the tool may be the same function, optionally compressed linearly by a factor, as the function FFt2 on the workpiece. The linear compression can relate to the argument of the function and/or to the magnitude of the function. In this respect, the sign of the function naturally changes between the workpiece and the tool since raised points on the tool produce lowered points on the workpiece and vice versa. In the normal section, in particular FFt1(x)=−FFt2 (cx) can apply in this respect, i.e. there is only compression with respect to the argument; an additional constant factor k can in contrast be present in the transverse section with respect to the magnitude of the function, i.e. FFt1(x)=−k*FFt2 (cx). The factors k and c can be larger than or less than 1 depending on the specific conditions.
In accordance with the present disclosure, different modifications may be produced on the left and right tooth flanks. The degree of freedom which is given by the cone angle of the tool having a conical basic shape may be used for this purpose. Modifications having a different alignment may be produced on the left and right tooth flanks. In this respect, in particular the first direction in which the modifications are constant can differ on the left and right tooth flanks in this respect.
The present disclosure furthermore may be used to machine or generate gear teeth of the workpiece which are asymmetrical on the left and right tooth flanks.
The machining of the workpiece may take place on two flanks in accordance with the present disclosure. In this case, both the left and the right tooth flanks are in contact with the tool during the gear manufacturing machining process. The two-flank generating machining has the advantage that the machining time can be substantially shortened with respect to a single-flank machining. The two-flank generating machining has the disadvantage, however, that the machining processes for the left and right flanks cannot be selected differently. It is in particular necessary for the left and right flanks to be worked with the same diagonal ratio. The provision of different modifications on the left and right tooth flanks of the workpiece is nevertheless made possible by the conical tool provided in accordance with the present disclosure.
In accordance with the present disclosure, the workpiece can have a cylindrical or a conical basic shape. In both cases, the conical tool in accordance with the present disclosure can be used.
In accordance with an embodiment of the present disclosure, the cone angle of the tool is greater than 1′, further optionally greater than 30′, and further optionally greater than 1°. Larger differences between the modifications on the right and left tooth flanks can also be produced by a correspondingly large cone angle.
The cone angle of the tool is, however, optionally less than 50°, optionally less than 20°, and further optionally less than 10°. This has technical production reasons, on the one hand, since the cone angle of the tool cannot be selected as any desired amount. The useful height of the tool is furthermore the smaller, the larger the cone angle of the tool with dressable tools to the extent that they are not anyway formed by grinding material applied to a conical base body.
In this respect, in accordance with the present disclosure, a desired alignment of the modification on the left and right tooth flanks may be achieved by a suitable selection of at least one, and optionally of a plurality of parameters of the machining process and/or of the macrogeometry of the tool, in particular of the diagonal ratio and/or of the axial cross angle and/or of the cone angle and/or of the profile angle of the tool. The present method in particular comprises a step of predefining a desired alignment of the modification on the left and right tooth flanks and of determining a parameter suitable herefor and/or of a combination of parameters of the machining process and/or of the macrogeometry of the tool suitable herefor.
In the machining process in accordance with the present disclosure, the axial feed of the tool may have a feed motion of the tool to the workpiece superposed on it. The superposed movement may take place in the direction of the cone. It is hereby achieved that the tool has the same engagement depth into the workpiece during the machining process despite the conical base shape. The feed motion in particular takes place in linear dependence on the axial feed. The proportionality factor between the axial feed and the feed motion of the tool may depend on the cone angle and optionally corresponds to the tangent of the cone angle.
In the method in accordance with the present disclosure in which a specific modification of the surface geometry of the tool is used to generate a corresponding modification of the surface geometry of the workpiece, the macrogeometry of the tool, in particular the cone angle and/or the profile angle of the tool and/or the line of action of the dressing tool and/or the diagonal ratio and/or the compression factor is/are optionally selected such that the modification of the tool along a first line on which the contact point moves on the machining of the workpiece on the tool corresponds to the desired modification of the workpiece along a second line on which the contact point moves on the workpiece. In this respect, with a given macrogeometry of the tool, the line of action of the dressing tool, the diagonal ratio and the cone angle can in particular be selected such that the first direction of the modification on the tool is mapped to the first direction of the desired modification on the workpiece.
In addition to the method in accordance with the present disclosure, the present disclosure furthermore comprises a tool for the gear manufacturing machining of a workpiece by a diagonal generating method, said tool having a conical base shape. The advantages which have already been described in more detail above result due to the tool in accordance with the present disclosure.
The tool may be a dressable tool. In a possible embodiment, the tool can have a base body on which a layer of grinding material is applied whose shape is variable by a dressing process.
In a possible embodiment, the base body can already have a conical base shape in order also to provide a uniform thickness of the available layer of grinding material with a conical base shape of the finished tool. The present disclosure can, however, also be used with tools having a cylindrical base body on which a cylindrical layer of grinding material is applied. There is hereby greater freedom in the choice of the cone angle.
The tool in accordance with the present disclosure can in particular be a grinding worm.
The cone angle of the tool in accordance with the present disclosure may be greater than 1′, further optionally greater than 30′, further optionally greater than 1°. The cone angle of the tool is further optionally less than 50°, optionally less than 20°, and further optionally less than 10°.
The tool in accordance with the present disclosure can have a specific modification of the surface geometry so that a corresponding modification on the surface of the workpiece can be produced by the mapping of the surface of the tool onto the surface of the workpiece produced by the diagonal generating method.
Provision can furthermore be made that the modification of the surface geometry of the tool furthermore has a constant value in the generating pattern at least locally in a first direction of the tool and is further optionally be given by a function FFt1 in a second direction of the tool which extends perpendicular to the first direction.
In accordance with the present disclosure, the modification of the tool can be identical or at least have the same orientation on the left and right flanks. Different modifications or differently oriented modifications are then optionally produced on the right and left flanks of the workpiece only via the cone angle.
In this respect, in accordance with the present disclosure, the modification can differ on the right and left flanks of the tool. The modification can in particular have different orientations, in particular different first directions, on the left and right flanks. Alternatively or additionally, the modification on the left and right flanks can be given by different functions FFt1 in the second direction. The different modifications on the left and right flanks of the workpiece which are produced by the method in accordance with the present disclosure thus result, on the one hand, from the different modifications on the right and left flanks of the tool and, on the other hand, from the conical basic shape of the tool.
The present disclosure furthermore comprises a gear manufacturing machine for carrying out a method in accordance with the present disclosure as was shown above.
The gear manufacturing machine in accordance with the present disclosure preferably has an input function via which the cone angle of the tool and/or of the workpiece can be input and/or changed.
The gear manufacturing machine further may have a control function which controls the NC axes of the gear manufacturing machine such that a tool having a conical basic shape rolls off on the workpiece in the diagonal generating method during the machining. In this respect, the axial feed of the tool may have a feed motion of the tool to the workpiece superposed on it. The superposed movement hereby resulting further optionally takes place in the cone direction.
Alternatively or additionally, the gear manufacturing machine can allow the dressing of a conical tool, where the gear manufacturing machine may have a control function for this purpose which controls the NC axes of the gear manufacturing machine such that the dresser follows the conical basic shape on the dressing of the tool having a conical basis shape.
The gear manufacturing machine in accordance with the present disclosure can furthermore comprise an input function which allows the input of a desired modification of the workpiece. A calculation function may also be provided in this case which determines the changes of the machine kinematics during dressing processes required for the production of the modifications and/or which determines the required cone angle and/or the required profile angle. In this respect, the changes of the machine kinematics which are superposed on the feed motion of the dresser to the tool predefined by the cone angle can in particular be calculated. The calculation function can furthermore calculate the required diagonal ratio.
Alternatively or additionally, the gear manufacturing machine can comprise an input function by which desired modifications of the tool and/or the required cone angle and/or the required profile angle and/or the changes of the machine kinematics required for producing these modifications can be input during the dressing process. They can then, for example, be calculated externally and supplied via the input function of the gear manufacturing machine.
The gear manufacturing machine further preferably has a control function which changes the machine kinematics accordingly during the machining process and/or the dressing process.
The gear manufacturing machine in accordance with the present disclosure can in particular be equipped with a conical tool such as was described further above.
The gear manufacturing machine in accordance with the present disclosure is further optionally a gear grinding machine. The gear grinding machine may have a tool spindle, a workpiece spindle and/or a spindle for the reception of a dresser, in particular of a dressing wheel, and machine axes for carrying out the relative movements required in accordance with the present disclosure between the workpiece and the tool and/or between the tool and the dresser in accordance with the present disclosure.
The gear manufacturing machine in accordance with the present disclosure further may have functions for carrying out a method in accordance with the present disclosure.
The present disclosure will now be explained in more detail with reference to embodiments and Figures.
The Figures only show w-z diagrams of cylindrical gear teeth by way of example.
The w-z diagrams of conical gear teeth are generally not rectangular, are typically trapezoidal, since the evaluation region of the generating path varies over the gear tooth width.